1. Field of the Invention
The present invention relates generally to an image forming apparatus. More particularly, the present invention relates to an image forming apparatus including ink jet type printing heads each adapted to eject ink therefrom to a cloth or a textile (hereinafter referred to simply as a cloth) usable as a printing medium for forming printed image on the printing medium with ink. Further, the present invention relates to an apparatus for fitting a conveying belt to an image forming apparatus of the foregoing type and removing the former from the latter. Moreover, the present invention relates to a method of fitting a conveying belt to an image forming apparatus of the foregoing type and removing the former from the latter.
2. Description of the Related Art
As a latest technology, an ink jet type textile printing apparatus has been increasingly known in the art. This type of textile printing apparatus has the advantageous effects based on a main reason that no original is required for an image to be printed on a printing medium in contrast with a conventional screen textile printing process. Specifically, one of the advantageous effects is such that the ink jet type textile printing apparatus has a high degree of freedom in respect of an image to be printed on the printing medium and the other one is such that the ink jet type textile printing apparatus can be produced at a low cost compared with the total textile printing installation.
A typical conventional ink jet type textile printing apparatus is disclosed in an official gazette of Japanese Patent Application Laying-Open No. 5-212851. As is apparent especially from FIG. 2 in the official gazette, each printing operation is performed by ejecting ink from a plurality of ink jet heads toward a cloth which is conveyed in the vertical direction. In other words, ink is ejected from the ink jet heads in the horizontal direction. A printer section including a plurality of ink jet heads and a conveying mechanism including an endless conveying belt are arranged in the printing section adapted to eject ink therefrom with a cloth held in the clamped state therebetween while they face to each other.
A tacky layer is placed on the surface of the endless conveying belt, and a cloth serving as a printing medium is adhesively attached to the tacky layer of the endless conveying belt to hold the cloth in the flattened state. Next, as the endless conveying belt is intermittently driven, the cloth is intermittently conveyed at a distance equal to a predetermined width.
After images are printed on the surface of the printing medium within the range defined by a single printing width in accordance with a hitherto known serial printing process, the cloth is pulled by a cloth winding roller disposed on the most downstream side of a conveying path while an adequate intensity of tensile force is applied to the cloth. As the cloth is conveyed further together with the endless conveying belt, it is peeled away from the tacky layer on the surface of the endless conveying belt, and subsequently, it is conveyed via a path as shown in the drawing and wound around the winding roller.
Next, immediately after the cloth is peeled from the endless conveying belt, part of the cloth having images printed thereon is dried by a drying unit for drying ink remaining on the cloth in the non-dried state. One of a process of blowing hot air to a cloth having images printed thereon, a process of irradiating infrared rays to a cloth and similar processes is adequately selected for the drying unit. This step of drying is especially effective in the case that a liquid printing agent is employed for each printing operation.
For example, as shown in FIG. 1, provided that confirming paths L for visually confirming the printed state images printed on the cloth is formed in the image forming apparatus between a head carriage 5010 having a plurality of ink jet heads 5100 mounted thereon and a drying unit 5600 both of which are spaced away from each other, an operator 80 can visually check printed images immediately after completion of each printing operation while handling an operation board or panel 5900 with his hand.
Therefore, even in the case that there arise malfunctions that ink can not be ejected from the ink jet heads 5100 due to clogging of the ink jet heads 5100 with foreign materials and abnormality occurs with the printed image, the operator 80 can visually observe printed image immediately after completion of each printing operation. This makes it possible to detect that the printing operation is incorrectly achieved, and moreover, prevent the incorrectly printed part from being enlarged by adequately handing the operation panel 5900 with an operator's hand without any delay.
In FIG. 1, reference numeral 5130 designates an endless conveying belt, reference numeral 5021 designates a winding roll, and reference numeral 5011 designates an unwinding roller for unwinding a cloth 1800 serving as a printing medium therefrom.
Generally, the printer section of the textile printing apparatus can slidably be displaced in the horizontal direction in order to assure that the distance between the printer section and the cloth can be adjusted as desired and the endless conveying belt can be exchanged with another one after the printer section is displaced.
Also with respect to the ink jet type textile printing apparatus as described above, many requests have been raised from users for improving a printing speed of the textile printing apparatus without any exception among various kinds of printer sections employable for textile printing apparatus.
In the case that the printing speed of the textile printing apparatus is to be improved under a condition that each textile printing operation is performed with a comparatively long continuous cloth, a method of most directly realizing the improvement of the printing speed is such that the number of ink ejecting nozzles formed in each ink jet head is increased, i.e., the length of each ink jet head is elongated. In more detail, the width of one line printed per single scanning performed with each ink jet head can be enlarged by increasing the number of ink ejecting nozzles arranged in the conveying direction of a printing medium such as a cloth or the like (i.e., by elongating the length of each ink jet head as measured in the conveying direction), whereby the printing speed of the textile printing apparatus can be improved by increasing a quantity of conveyance of the printing medium corresponding to the enlarged width of each printed line.
In the case that each ink jet head in the textile printing apparatus as disclosed in the official gazette of the aforementioned prior invention is designed to have a longer length, ink ejecting nozzles in each ink jet head are arranged in the vertical direction, causing a difference in pressure head between adjacent ink ejecting nozzles to become comparatively large. This difference in pressure head between adjacent ink ejecting nozzles is expressed in the form of a difference in a quantity of ejected ink between adjacent ink ejecting nozzles, resulting in a quality of printed image being degraded.
On the other hand, a textile printing apparatus including a plurality of ink jet heads each adapted to eject ink in the downward direction, i.e., including a plurality of so-called downward orienting ink jet heads as disclosed in an official gazette of Japanese Patent Application Laying-Open No. 5-31905 filed by an applicant to the present invention has been known in the art. According to this prior invention, the aforementioned problems in connection with the difference in pressure head between adjacent ink ejecting nozzles can be solved because ink ejecting nozzles in each ink jet head are arranged in the horizontal direction.
Advantageous effects derived from the downward orienting ink jet heads are such that recovering treatment can uniformly be conducted for all ink ejecting nozzles by ink suction or the like in connection with the equality in pressure head between adjacent ink ejecting nozzles, and moreover, invasion of water droplets adhering to an ink ejecting plane into the ink ejecting nozzles can reliably be prevented.
However, when the downward orienting ink jet heads are used for the textile printing apparatus as they are, it is anticipated that various kinds of problems appear due to factors specific to this type of textile printing apparatus.
As far as the textile printing apparatus is concerned, the distance between the ink jet heads and the cloth (head gap) should adequately be adjusted corresponding to the thickness of a various kind of cloth to be used. In addition, to assure that the endless conveying belt is easily exchanged with another one, it is desirable that all of the ink jet heads (i.e., the whole printer section) can easily be displaced from the printing position. However, in contrast with a printer for business use or personal use, the textile printing apparatus including a plurality of downward orienting ink jet heads has problems that the printer section is constructed with larger dimensions and heavy weight and it is not easy to conduct adjustment and displacement for the textile printing apparatus for the reason that the ink jet heads and the belt conveying section are located opposite to each other in the vertical direction.
Further, to suppress an occurrence of incorrect printing operation, it is necessary that an operator can quickly confirm a quality of printed image after completion of each printing operation. In the case that a plurality of downward orienting ink jet heads are used for the textile printing apparatus, as shown in, e.g., FIG. 2, it is necessary that a printing medium 1800 can be conveyed in the horizontal direction while a plurality of ink jet heads 5100 face to a conveying belt 5131.
To assure that the printed state of images printed on the printing medium 1800 conveyed in the horizontal direction by the conveying belt 5131 can be confirmed immediately after the images are printed on the printing medium 1800, it is thinkable that a conveying path upwardly extending from a downstream end 5132 of the conveying belt 5131 at a substantially right angle relative to the conveying plane of the conveying belt 5131 is formed in the folded state, and the printed state of images can visually be confirmed by an operator 80 via confirmation paths L as shown in FIG. 2.
However, since a high intensity of tension is applied to the printing medium 1800 via a winding roller 5021, causing the printing medium 1800 to be forcibly pulled by the winding roller 5021, there arise problems that the printing medium 1800 is sharply bent immediately after it is peeled from the tacky layer of the conveying belt 5131 at the downstream end 5132 of the conveying belt 5131, and printed images which are not still perfectly dried immediately after completion of each printing operation are disturbed or deformed.
In addition, there arises another problem that a line-shaped bent track appears on the printing medium 1800 or the printed images due to bending of the printing medium 1800 at the downstream end 5132 of the conveying belt 5131.
Provided that a guide roll having a certain diameter is disposed at the position located inside of the folded line in order to prevent the printing medium 1800 being sharply folded, the guide roll comes in contact with the printing plane of the printing medium 1800. This leads to the result that images printed on the printing medium 1800 are disturbed or deformed prior to drying treatment.
In the case that any guide roll can not be disposed at the position located inside of the folded line and properties of the tacky layer on the conveying belt 5131 are deteriorated due to repeated use of the conveying belt 5131 for a long time, the printing medium 1800 is peeled from the conveying belt 5131 at a point 5133 located upstream of the downstream end of the printing medium 1800, resulting in the conveying path being bent as represented by a phantom line 1801. This leads to the result that printed images are disturbed or deformed prior to drying treatment due to rubbing contact of the printing medium 1800 with a drying unit 5600, a printer frame 5050 or a similar component.
In the case that a plurality of ink jet heads each having a number of ink ejecting nozzles arranged as printing elements therein are used for the textile printing apparatus, to prevent the density of each printed image from fluctuating from image to image attributable to fluctuation in a quantity of ink ejected from each ink ejecting nozzle, a certain unit may be arranged in the textile printing apparatus for forming a test pattern on an adequate printing medium, measuring the fluctuation in a quantity of ejected ink by optically reading the test pattern, and then obtaining data required for correcting the fluctuation in a quantity of ejected ink. However, when a measure is taken so as to allow a series of steps as mentioned above to be easily practiced, the textile printing apparatus is unavoidably constructed with larger dimensions due to the arrangement of the foregoing unit. In practice, it is desirable that the textile printing apparatus is not constructed with large dimensions.